This application is based on and claims priority under 35 U.S.C. xc2xa7119 with respect to Japanese Patent Application No. 2000-263706, filed on Aug. 31, 2000, the entire content of which is incorporated herein by reference.
This invention generally relates to a control device for controlling an actuator applied in a vehicle transmission.
Vehicles such as passenger cars, buses, trucks and the like are generally driven by a driving power source such as, for example, an engine or an electric motor. Further, the vehicle includes a transmission and is applied with a driving speed and a driving force corresponding to a vehicle running condition. Known transmissions include an automatic transmission (AT), a continuously variable transmission (CVT), and a manual transmission (MT).
The known manual transmission is provided with a counter shaft (an input shaft), a main shaft (an output shaft), a plurality of counter gears mounted on the counter shaft, a plurality of idle gears mounted on the main shaft, and a synchromesh mechanism. The counter shaft is a transmitting member that transmits input rotation of the engine to the main shaft (the output shaft). The main shaft is a transmitting member for the output rotation of the transmission to a propeller shaft. The plurality of idle gears is idly rotated around the main shaft and is always engaged with the plurality of counter gears. The synchromesh mechanism includes synchronizer hubs that are mounted on the main shaft and are rotated integrally with the main shaft. The synchromesh mechanism further includes sleeves which mesh with splines defined in the outer surface of the synchronizer hub so that the sleeve is slidably movable in the axial direction of the main shaft. More specifically, the synchromesh mechanism selectively operates one of the sleeves to slidably move on the main shaft on the basis of a driver""s intention. The spline-engagement between the sleeve (i.e. the main shaft) and the idle gear synchronize rotation of the selected sleeve (i.e. a rotation of the main shaft) with a desired rotation of the idle gear so that a desired speed-change is performed.
According to the known manual transmission, operation of the clutch by the driver is required to permit a shift operation by the driver to perform the desired speed-change. When a floor-mounted shift lever or a column shift lever is operated by the driver to perform the desired speed-change upon shift operation, a shift fork shaft and a shift fork are moved in response to the operation of the shift lever. The sleeve engaged with a tip end of the shift fork is slidably moved so as to perform the desired speed-change.
Somewhat recent developments have led to automatic manual transmissions which are structurally based on the manual transmission (MT). The automatic manual transmission performs an automatic shift operation based on the vehicle driving condition or a semiautomatic shift operation based on the driver""s intention. Therefore, the automatic manual transmission effectively decreases the operating load or operating requirements of the driver. This type of automatic manual transmission requires an actuator as a substitute for the manual operation performed by the driver in case of the manual transmission. The actuator is activated by a driving power source such as hydraulic pressure, air pressure, or an electric motor. Whichever driving power source is used for the actuator, it is preferable that the actuator be adapted to effect a relatively complex, fine, and proper control in order to decrease shift shock.
For example, when the actuator is activated by hydraulic pressure, the amount of electric current supplied to a solenoid valve such as a linear solenoid valve needs to be relatively finely controlled. Further, the timing associated with the supply of electric current to the solenoid valve also needs to be relatively finely controlled so that the hydraulic pressure supplied to the actuator is properly controlled. On the other hand, when the actuator is activated by an electric motor such as a servo motor or a stepping motor, the amount of electric current supplied to the electric motor needs to be relatively finely controlled. Further, the timing associated with the supply of electric current to the electric motor also needs to be relatively finely controlled so that the timing of the actuator to be activated and the load applied to the actuator are properly controlled. The description that follows is based on an actuator that is activated by an electric motor.
The amount of electric current supplied to the electric motor is limited and varies depending on the vehicle environment or the vehicle driving condition. For instance, a maximum electric current value supplied to the electric motor varies depending on the temperature difference between the temperature immediately after an initial driving of the electric motor and the temperature after continued driving of the electric motor, the battery voltage accommodated in the vehicle, and the characteristics of the electric motor. The amount of electric current supplied to the electric motor may sometimes vary by approximately 30-50% depending on such factors. Therefore, it may not be possible to control the electric motor with the original design performance and so shift shock may occur.
More specifically, as shown in FIG. 5, because the maximum electric current value actually supplied to the DC motor is lower than a predetermined target electric current, a relatively large difference may exist between the target electric current value and an actual electric current value. Therefore, shift shock may occur due to an error with respect to the speed or timing of a shift stroke. As shown in FIG. 6, a proportional increase of the electric current up to a value I1 is expected to perform for the period t1 (depicted with a dashed line). However, because the maximum electric current value supplied to the DC motor is only I2, the proportional increase of the electric current to the value 11 is not performed. The proportional increase of the electric current up to the electric current value 12 is performed for the period t2. Further, the electric current value supplied to the DC motor after t2 is maintained at the value 12. Therefore, the operation of the actuator is unstable due to a surge load, wherein the shift shock may occur.
It is thus seen that known vehicle automatic manual transmissions are susceptible of certain improvements with respect to providing an improved control device that performs accurate control of the actuator driven by an electric current to reduce shift shock.
A need this exists for an improved control device for controlling an actuator applied in a transmission and activated by electric current supplied to a motor.
A need also exists for an improved control device which is adapted to detect a maximum electric current value actually supplied to the actuator and control the actuator on the basis of the detected maximum electric current value.
A need also exists for an improved control device which determines a target electric current value to be supplied to the actuator on the basis of a set maximum electric current value and avoids or decreases a difference between the target electric current value and the actually supplied electric current value to thereby perform a relatively stable operation of the actuator by decreasing the shift shock.
A control device for an actuator of a vehicle transmission includes a target electric current value determining mechanism for determining a target electric current value to be supplied to the actuator, an electric current supplying mechanism for supplying an electric current to the actuator based on the target electric current value, a maximum electric current value detecting mechanism for detecting a maximum electric current value actually supplied to the actuator regardless or independent of the target electric current value, and a maximum electric current value setting mechanism for setting the maximum electric current value based on the maximum electric current value detected by the maximum electric current value detecting mechanism.
The control device for the actuator can further include a malfunction indicating signal outputting mechanism that outputs a malfunction indicating signal when the maximum electric current value output by the maximum electric current value setting mechanism deviates from a predetermined allowable range. When the malfunction indicating signal is outputted by the outputting mechanism, the control mode can be changed to a fail-safe mode.
The actuator can be in the form of a DC motor and the control device for the actuator can also include a temperature detecting mechanism for detecting an ambient temperature of the DC motor. The maximum electric current value detected by the maximum electric current value detecting mechanism is based on the ambient temperature detected by the temperature detecting mechanism.